The objective of this research is to partially purify the mouse liver glucocorticoid receptor and to prepare monoclonal antibodies to the receptor using the hybridoma technique of Milstein. Purification is being accomplished by DNA-cellulose and DEAE chromatography. Hybrid cells prepared by fusing spleen cells from an immunized mouse with a permanent cell line such as P3-X63-Ag8 will be cloned in soft agar. Clones producing anti-receptor antibody will be detected by immunoprecipitation of labeled receptor preparations.